1. Field of the Invention
The present invention relates to a thermosetting resin composition, and more particularly to a thermosetting resin composition excellent in processability, heat resistance and adhesive property.
Further, the present invention relates also to a composite material excellent in mechanical strength at high temperature and in hot water resistance which comprises cured product of said thermosetting resin composition as its matrix.
2. Description of the Prior Art
Thermosetting resins are used as materials for casting, impregnation, lamination and molding in the fields of electrical insulation, construction, etc. In these fields, there is a current tendency that the conditions under which these materials are used become more and more severe. Particularly, an increasing importance is being attached to heat resistance of material.
Hitherto, thermosetting polyimide resin and heat resistant epoxy resin have been used for such purposes.
However, polyimide resin is disadvantageous in that its processing requires a longterm heating at a high temperature. Although epoxy resin having an improved heat resistance is excellent in processability, it is also disadvantageous in that it is insufficient in the high-class heat resistances, i.e. mechanical and electrical properties at high temperatures.
As a material capable of replacing them, there was proposed in Japanese Patent Kokai (Laid-Open) No. 154,897/77 a thermosetting mixture comprising a polyimide, an allyl group-containing epoxy compound having a special structure and a curing agent. However, the allyl group-containing epoxy compound used therein was a compound prepared by subjecting an allyl ether compound to Claisen rearrangement and then epoxidizing the rearranged product, from which a uniform cured product is difficult to prepare probably because the nucleus-substituting allyl group and epoxy group are located on the ortho positions of one aromatic ring. Particularly in the case of novolac type, this type of compositions were inferior in physical properties and heat resistance of cured product probably because some of these groups are apt to remain unreacted.
Further, in Japanese Patent Kokai (Laid-Open) No. 134,099/78, there was proposed a heat resistant resin composition comprising a specified maleimide compound, a polyallyl phenolic compound, an epoxy resin and a curing agent. However, this composition was inferior in electrical properties at high temperatures and resistance to thermal deterioration because the polyallyl phenolic compound used therein had a phenolic hydroxyl group or had a structure capable of forming a phenolic hydroxyl group by Claisen rearrangement when the composition was heated and cured. Thus, in order to overcome such a fault, the composition had to contain an epoxy resin and a curing agent capable of reacting with phenolic hydroxyl group, due to which the composition decreased its heat resistance.
On the other hand, composite materials containing a fiber as a reinforcing material have a high tensile strength and a high elastic modulus, owing to which its use is expanding in various fields such as structural materials of aircrafts and automobiles, constituent parts of engines, etc.
As the matrix phase material of these composite materials, thermosetting resins, particularly epoxy resins, have been used mainly for the reason of their good moldability and physical properties.
However, since composite materials have become applicable to more and more extensive fields in the recent time, it is desired today to develop a new material capable of retaining the high chemical stability and the good mechanical properties even at a temperature exceeding the temperature range in which the conventional composite materials containing an epoxy resin as their matrix are put to use. Thus, the use of various resins including polyimide resin as the matrix has been studied. However, all the resins hitherto studied are disadvantageous in that they are difficult to mold, and molded products prepared therefrom tend to contain vacancies, and some of them are inferior in adhesive strength between matrix and reinforcing material and therefore cannot give a product of high strength.
Considering the above-mentioned background, the present inventors conducted earnest studies to find that a resin composition comprising a specified resin and a polymaleimide compound having two or more maleimide groups in one molecule is excellent in heat resistance and processability and can satisfy the above-mentioned requirements.
Further, the present inventors also found a fiber reinforced composite material excellent in moldability and strength, capable of retaining its high strength even at high temperatures and having an excellent hot water resistance can be obtained by using, as the matrix phase, cured product of a resin composition comprising a polymaleimide compound having two or more maleimide groups in one molecule and a phenol novolac resin of which phenolic hydroxyl groups are epoxidized and allyl-etherified optionally containing a curing agent, too) or cured product of a resin composition comprising a polymaleimide compound having two or more maleimide groups in one molecule, a phenol novolac resin of which phenolic hydroxyl groups are allyl-etherified and an epoxy resin and using a fiber as a reinforcing material.
Based on the above-mentioned findings, the present invention was accomplished.
According to the present invention, there is provided a thermosetting resin composition comprising a polymaleimide compound having two or more maleimide groups in one molecule and a phenol novolac resin of which phenolic hydroxyl groups are epoxidized and allyl-etherified, and optionally a curing agent.
Further, according to the present invention, there is also provided a thermosetting resin composition comprising a polymaleimide compound having two or more maleimide groups in one molecule, a phenol novolac resin of which phenolic hydroxyl groups are allyl-etherified and an epoxy resin.
Further, according to the invention, there is also provided a heat resistant composite material containing, as its matrix, cured product of a resin composition comprising a polymaleimide compound having two or more maleimide groups in one molecule and a phenol novolac resin of which phenolic hydroxyl groups are epoxidized and allyl-etherified and optionally a curing agent, and containing a fiber as the reinforcing material.
Further, according to the present invention, there is also provided a heat resistant composite material containing, as its matrix, cured product of a resin composition comprising a polymaleimide compound having two or more maleimide groups in one molecule, a phenol novolac resin of which phenolic hydroxyl groups are allyl-etherified and an epoxy resin and containing a fiber as its reinforcing material.